The present invention relates to an apparatus and a method for transporting goods, in particular to an apparatus and a method as used in the field of paper handling for supplying goods to processing, wherein the goods can be flat goods, for example filled envelopes, packaging, groups of products, sheets or groups of sheets.
Apparatuses for transporting and processing envelopes are known in conventional technology. Such apparatuses comprise, for example, a printer for printing a surface of a filled envelope, for example an address, other information, advertising or also for franking the envelope. In such known apparatuses that are to effect processing of the transported goods, it is necessitated that the goods are moved at a predetermined distance with respect to the processing station; in the case of a printer, it is necessitated to maintain a predetermined distance between the surface of the envelope and the print heads of the printer to ensure proper printing. In other examples, the envelope is supplied to the processing station, and it is desirable that the envelope is, with its top surface, in a specific relation with respect to the inlet of the processing station. The processing station can, for example, be a franking unit, a labeler, a laminator or a coater.
As long as the goods to be processed have the same thickness, maintaining the distance between processing station and the surface of the goods item presents no problem, since all elements of the apparatus can be adjusted accordingly. However, in the field of paper handling, envelopes having differing thickness result when generating items of mail, depending on how heavily and with what the envelopes are filled. This has the effect that envelopes provided by an enveloper have varying thicknesses, so that no constant distance is given between the processing station and the surface of the envelope.
In the case of printers, it can, for example, be intended in this situation to contact the filled envelopes in edge areas of the same by a top guide, wherein the top guide is adjusted such that a distance of the envelope to the processing station corresponds to a desired distance and hence proper printing can be ensured in most cases. However, it is a disadvantage of this implementation that, due to the top guides engaging, for example, laterally with the transported envelope, not the complete surface of the envelope is available for printing and an edge area remains free. Further, the envelopes can contain goods causing irregular thickness distribution across the width and the length of the envelope, so that, particularly in the case of lateral top guides acting only on the edge areas of the envelope, varying thicknesses exist in the area between the guides, which has the effect that, at least partly, the distance to the processing station is less than the desired or necessitated distance, so that problems in printing can arise despite the guide. Although this can be suppressed by dimensioning the guides accordingly or by providing further guiding elements, the printable area on the surface of the envelope or goods item is limited even further thereby.
A further approach known in conventional technology is to detect the thickness of the goods item prior to its transport and further processing and, depending thereon, to move either the transport, the processing station or both relative to one another so that the desired distance from the surface to a reference plane can be adjusted dynamically for the goods item to be processed. FIG. 1 shows a schematic illustration of a plant for processing flat goods as is used in conventional technology. FIG. 1 shows a transport 100 comprising a belt 104 running around two rollers 102a and 102b. Instead of the shown belt, other elements can be used, for example chains having appropriate grippers or the like, as is known in conventional technology in general. The rollers 102a and 102b are pivoted across the bearings 106a, 106b, wherein one of the rollers 102a or 102b is driven by a drive not illustrated in FIG. 1. The transport 100 is arranged in a height-adjustable manner indicated by arrows 108a, 108b. Further the transport 100 comprises rollers 112a, 112b defining, together with the rollers 102a or 102b, a roller pair to determine a transport inlet or a transport outlet.
The plant shown in FIG. 1 further comprises a processing station 200 including, in the example shown, a printer 202 comprising print heads 202a, 202b. The printer can, for example, be an ink jet printer. Similarly to the transport 100, the printer is also arranged in a height-adjustable manner, as is indicated by the arrow 204.
At the inlet 102a, 112a the plant receives the goods passed along the processing station 200 by means of the transport 100 to effect printing of a top surface of the goods. At the input, the plant includes the sensor S to detect the thickness of the goods item, so that, depending on the thickness, either the height position of the transport 100 and/or the height position of the printer 202 can be adjusted such that a desired distance a between the print heads 202a, 202b and the surface of the goods item G on the transport is maintained and hence proper printing can be ensured.
With respect to the above-described approach including top guiding elements for guiding the goods item G, the approach according to FIG. 1 is advantageous, since these top guiding elements can be omitted, so that printing the goods item across its whole area becomes possible. However, the approach of FIG. 1 necessitates significant mechanical effort to either move the transport 100, the printer 202 or both depending on a detected thickness of the goods item. This is also time-consuming since it might necessitate changing the adjustment for each of the goods. Printing can only take place when the adjustment has been completed. Further, the approach shown in FIG. 1 allows only the transportation of a single goods item, since the thickness is detected for each item and respective adjustment is made, so that the throughput, i.e. the number of processed goods per time unit, suffers. Further, there is a problem when the goods have a thickness that varies along the width of the goods item or along the length of the goods item (in the transport direction T), since in this case the sensor might detect only an average thickness of the goods item and thus no optimum distance exists in all areas of the surface of the goods with respect to the print head and thus non-optimum printing takes place.